With continuous progress of communications technologies, users are imposing an increasingly high requirement on voice quality. Generally, voice quality is improved by increasing bandwidth of the voice quality. If a signal whose bandwidth is wider is encoded in a traditional encoding manner, a bit rate is greatly improved and as a result, it is difficult to implement encoding because of a limitation condition of current network bandwidth. Therefore, encoding needs to be performed on a signal whose bandwidth is wider in a case in which a bit rate is unchanged or slightly changed, and a solution proposed for this issue is to use a bandwidth extension technology. The bandwidth extension technology may be completed in a time domain or a frequency domain. A basic principle of performing bandwidth extension in a time domain is that two different processing methods are used for a low band signal and a high band signal.
In the foregoing technology of performing bandwidth extension in a time domain, the high band signal is restored in a condition of a specific rate, however, a performance indicator is deficient. It may be learned by comparing a frequency spectrum of a voice signal that is restored by decoding and a frequency spectrum of an original voice signal that, a restored voice signal sounds rustling and a sound is not clear enough.